Numerical study on the characteristics of roadway failure and instability in coal seam with rock parting.

In order to explore the mechanism of rockburst in coal seam with rock parting, a combination of on-site and numerical experiment is used to study the failure and instability process, crack propagation mechanism, and influencing factors. The following four points were addressed: (1) the instability is a process that roadway in coal seam with rock parting go through from stable locking in the initial stress unloading stage to slipping unlocking, and then to spatter ejection in slipping dynamic load disturbance stage. (2) The fracture development caused by unloading excavation of coal seam with rock parting will change from shear crack to tensile crack. In this process, coal-rock contact surface slip and coal-rock fracture are coupled with each other. (3) The greater the mining depth is, the greater the lateral pressure coefficient is, and the higher the rockburst risk is. On the contrary, the lower the risk of rockburst. (4) When choosing the support form of roadway in coal seam with rock parting, the two supporting forms of bolting (cable) and supplementary masonry support should be preferred. The results enrich the theory of the dynamics of surrounding rock fracture in coal mine, further clarify the potential dangers to mining-area roadways and working faces, and provide technical information to ensure the safe and efficient mining of bifurcated coal seam.

SCF/c-Kit-activated signaling and angiogenesis require Gαi1 and Gαi3.

The stem cell factor (SCF) binds to c-Kit in endothelial cells, thus activating downstream signaling and angiogenesis. Herein, we examined the role of G protein subunit alpha inhibitory (Gαi) proteins in this process. In MEFs and HUVECs, Gαi1/3 was associated with SCF-activated c-Kit, promoting c-Kit endocytosis, and binding of key adaptor proteins, subsequently transducing downstream signaling. SCF-induced Akt-mTOR and Erk activation was robustly attenuated by Gαi1/3 silencing or knockout (KO), or due to dominant negative mutations but was strengthened substantially following ectopic overexpression of Gαi1/3. SCF-induced HUVEC proliferation, migration, and capillary tube formation were suppressed after Gαi1/3 silencing or KO, or due to dominant negative mutations. In vivo, endothelial knockdown of Gαi1/3 by intravitreous injection of endothelial-specific shRNA adeno-associated virus (AAV) potently reduced SCF-induced signaling and retinal angiogenesis in mice. Moreover, mRNA and protein expressions of SCF increased significantly in the retinal tissues of streptozotocin-induced diabetic retinopathy (DR) mice. SCF silencing, through intravitreous injection of SCF shRNA AAV, inhibited pathological retinal angiogenesis and degeneration of retinal ganglion cells in DR mice. Finally, the expression of SCF and c-Kit increased in proliferative retinal tissues of human patients with proliferative DR. Taken together, Gαi1/3 mediate SCF/c-Kit-activated signaling and angiogenesis.

Two New Secondary Metabolites from Tephrosia purpurea.

Further investigation of Tephrosia purpurea led to the isolation of a new prenylated flavone, isoglabratephrin B (1) and a new 1,2-ethanedione benzofuran derivative, purpdione B (2). The structures of the new isolates were elucidated on the basis of extensive spectroscopic analysis.

[Chemical Constituents of Seaweed Sargassum naozhouense].

OBJECTIVE: To investigate the chemical constituents in the seaweed Sargassum naozhouense collected from the sea around Zhanjiang. METHODS: The compounds were isolated and purified by various chromatographic techniques including silica gel chromatography, Sephadex LH-20 gel chromatography as well as preparative thin layer chromatography, and their structures were identified by spectral analysis. RESULTS: Ten compounds were isolated and identified as 1-O-hexadecanoyl glycerol (1), pheophytin a(2), ß-sitosterol (3), mannitol (4), uracil (5), thymine(6),p-hydroxybenzoic acid(7) 3,4-dihydroxybenzoic acid (8) 4-hydroxyphthalide (9), and 2'-de-cxythymidine( 10). CONCLUSION: All the compounds are isolated from the seaweed Sargassum naozhouense for the first time.